1. Field of the Invention
The present invention relates to a CMP conditioner that is used in the conditioning of polishing pads of a chemical mechanical polishing (CMP) apparatus that polishes semiconductor wafers and the like.
Priority is claimed on Japanese Patent Application No. 2004-274912, filed Sep. 22, 2004, the contents of which are incorporated herein by reference.
2. Description of Related Art
For this type of CMP conditioner, a technology has been proposed, for example, in patent document 1 (Japanese Unexamined Patent Application, First Publication No. 2001-71267) in which, in a pad conditioning diamond dresser in which a single layer of diamond grit is adhered to a base metal operating surface of a disk-shaped or cup-shaped base metal by nickel plating, 70% or more of the adhered diamond grit has ridges or peaks of crystals as protruding ends. Moreover, in patent document 2 (Japanese Unexamined Patent Application, First Publication No. 2002-273657), technology has been proposed in which, in a CMP processing dresser in which diamond grit has been adhered to the surface of a base material by brazing, those projection lines of the vertical lines of the {111} face of the diamond grit crystals that are projected towards the dresser substrate fixing surface are substantially parallel with the dresser grinding direction, or this {111} face is at an angle of 15 to 75 degrees relative to the grinding surface of the polishing cloth.
However, firstly, if, as is the case in the patent document 1, a majority of the adhered diamond grit is adhered such that the protruding ends are formed by ridges or peaks of the crystals of the diamond grit, namely, by sharp portions where surfaces of adjacent crystals intersect on the surface of the diamond grit, in other words, if a majority of the diamond grit is adhered so as to protrude from the conditioning surface that is in contact with the polishing pad of the CMP apparatus in the direction faced by this conditioning surface, then although the sharpness of the grit in the initial stages of the conditioning is high and a high rate of pad polishing can be obtained, the sharp portions that form the aforementioned protruding ends end up losing their sharpness at a very early stage due to the speed of the abrasion so that the polishing rate deteriorates markedly. As a result, the lifespan of the CMP conditioner is far less than it should be. Moreover, if the ridge portions and, in particular, the peak portions of the crystals form protruding ends in this manner, as is described above, these portions end up being lost before they are worn out so that there is a possibility that the chipped fragments thereof will scratch the surface being polished of the semiconductor wafer or the like that is being polished by a CMP apparatus, and that scratches will be generated in the surface that is being polished.
On the other hand, in the CMP conditioner described in the patent document 2, for example, by making the protrusion heights and contact surfaces of each piece of grit on the {001} surface of hexahedral or octahedral diamond grit the same in a direction towards the surface of the base material, namely, towards the conditioning surface and in parallel with this conditioning surface, it is possible to make the load uniform on each piece of grit and prevent chipped fragments from being generated. In addition, by brazing the grit pieces such that, as is described above, the projection lines of the vertical lines of the {111} face are substantially in parallel with the grinding direction or, alternatively, are diagonally inclined at the aforementioned angle relative to the grinding surface, then by placing this {111} surface, which has a high degree of strength, in contact with the grit on an abrasive cloth (i.e., a polishing pad) as a cutting edge, dressing can be performed effectively, and it is difficult for chipped fragments to be generated. Moreover, scratching of the surface being polished is prevented.
However, conditioners that are used in a CMP apparatus are placed on the rotating polishing pad of the CMP apparatus so as to be in contact with the conditioning surface, and the CMP conditioner itself is rotated around a different axis from the rotation axis of the polishing pad, and is also oscillated on the surface of this polishing pad. As a result, it is not always certain that the projection lines of the vertical lines of the {111} surface of the grit that has been brazed to the conditioning surface will be parallel to the grinding direction. Moreover, if, for example, conditioning is performed with a surface other than the {111} surface facing entirely in the grinding direction, then wear occurs in the ridge lines and peak portions of this surface and the surface other than the {111} surface that is the protruding end surface of the grit and the polishing rate is markedly reduced at an early stage. In addition, chipped fragments occur in these ridge lines and peak portions and the occurrence of scratching is unavoidable.